THE EFFECT OF CALCIUM ON THE CONTENT OF PROLINE AND SOLUBLE-PROTEINS IN PLANTS ACCLIMATING TO LOW-TEMPERATURE

The total content of Ca2+, free and bound proline, soluble proteins, a nd electrolyte efflux into water extract were investigated in the wint er wheat (Triticum aestivum L.) tissues of field-grown tillering plant s and of 7-day-old seedlings grown in water culture. Plants were diffe rentially supplied with calcium in the course of long-term (weeks) acc limation under field conditions and during short-term hardening (2-deg rees-C, three days) under controlled conditions. Under field condition s, a negative correlation was revealed between the accumulation of fre e proline and the level of Ca2+. At the same time, the correlation bet ween the content of calcium and the level of soluble proteins was posi tive. A decrease in the content of Ca2+ that restricts the consumption of free proline in the synthesis of soluble proteins is supposed to b e one of the reasons for the accumulation of free proline in cells aft er autumnal hardening. Under controlled hardening conditions (2-degree s-C, three days), this relationship remained valid. The tissues of see dlings grown on calcium-containing medium accumulated more soluble pro teins and less free prohne. A more pronounced accumulation of soluble proteins in the tissues of experimental plants supplied with Ca2+ sugg ests that calcium participates in the process of hardening as an adapt ive factor ensuring a higher level of frost resistance in plants. Upon freezing (-9-degrees-C, five h), Ca2+ no longer plays its adaptive ro le, and the destruction of proteins may be the main reason for the acc umulation of free proline.